1. Field of the Invention
The present invention relates to a modem and a method, and more particularly to a modem and a method for controlling the same, capable of transmitting and receiving data through the installation between a subscriber terminal and a switching system.
The present application is based on Korean Patent Application No. 2000-54945, filed Sep. 19, 2000, which is incorporated herein by reference.
2. Description of the Related Art
Various related art network communication service technologies have been introduced for providing high-speed communication services to users. For example but not by way of limitation, technologies such as the Asymmetric Digital Subscriber Line (ADSL), Bluetooth and Phoneline Network Alliance (PNA) have been applied for the network communication service technologies.
A subscriber modem is installed between a subscriber terminal and a switching system, relaying connections to a public network and performing communication relays between the subscriber terminal and the switching system.
The service method of the ADSL, which is a network communication service technology, can transmit data at a high speed through an existing telephone line. Because the ADSL service method uses the existing telephone lines, ADSL is widely used. Further, ADSL provides a downstream transmission rate of over 8 Mbps and an upstream transmission rate of over 1 Mbps.
Physically, ADSL is classified into a central service part managed with telephone lines connected thereto (e.g., a switching system), and a part for connecting a data backbone network to the central service part and a subscriber service part.
FIG. 1 illustrates an ATM switching system 20 connected to a subscriber terminal 10 through a subscriber's ADSL modem 30 in a general ADSL communication service system. The modem 30 converts data received from the subscriber terminal 10 (e.g., a user's personal computer) into a format required in the switching system 20 and transmits the converted data to the switching system 20. The modem 30 also converts data received from the switching system 20 into a format required in the subscriber terminal 10, and outputs the converted data to the subscriber terminal 10.
The modem 30 also maintains a communication channel with the switching system 20 to process data transmissions and receptions between the switching system 20 and subscriber terminal 10 at any time, regardless of data receptions from the subscriber terminal 10. Accordingly, the modem 30 transmits a signal for maintaining a channel periodically to keep the channel with the switching system 20, and the switching system 20 transmits a signal confirming the maintaining of the channel by the modem 30.
However, the conventional modem 30 has various problems and disadvantages. For example, the conventional modem 30 consumes unnecessary power to maintain a channel with the switching system 20 if the subscriber terminal 10 is in a non-connection status (i.e., powered off), or if the subscriber terminal 10 is in the non-connection status for a long time period when the subscriber terminal 10 does not communicate with an external network via the modem 30. As a result, the life span of the apparatus is shortened due to the above-described unnecessary operations.
Additionally, the driving mode of the conventional modem 30 affects the switching system 20 connected to a plurality of modems 30. The switching system 20 connected to the plurality of subscriber terminals 10 causes unnecessary power losses of the switching system 20, since the switching system 20 processes a signal for maintaining a channel of the plurality of subscriber's modems 30 when the channel maintaining signal is inputted from the plurality of subscriber's modems 30 in the non-connection status with the subscriber terminal 10. Thus, the utilization efficiency of communication lines and communication speed is restrained due to the unnecessary occupation of the communication lines.